Here is a quote from a speech given by Winston Churchill at Harvard University. "We have learned from hard experience that stronger, more efficient, more rigorous world institutions must be created to preserve peace and to forestall the causes of future wars. In this task the strongest victorious nations must be combined, and also those who have borne the burden and heat of the day and suffered under the flail of adversity; and, in this task, this creative task, there are some who say: "Let us have a world council and under it regional or continental councils," and there are others who prefer a somewhat different organisation." The interesting thing about this passage is that it is defending the idea of the United Nations, which many on the right seem to be vehemently against. However, Churchill was one of the greatest leaders of all time, and was not a pacifist. Perhaps critical self-reflection is in order.
It's not necessary that a nation belong to some world organization in order to avoid conflict. It just takes skillful negotiation, diplomacy, and yes... the willingness to engage in armed conflict as a last resort. IMO, participation with organizations like the U.N. only entangles us in politics and conflicts that we'd be better off avoiding. Also, I'm not too fond of the idea of a world organization influencing the future of individual nations... including our own. I don't like the idea of world organizations which become too powerful and agenda driven.
Churchill was not a great leader by any stretch of the definition. He was simply the man in office during the war. Anybody can give great speeches during times of war. Heck, Bush gave what's considered one of the best speeches in American history after 9/11 but that doesn't make him a great leader. Churchills actual policies were horrendous.
He was kicked out of the Navy for screwing up so bad. He screwed up the British economy and was considered weak on foreign affairs not having to do with the wars.